I don't have a favourite "brand". A brand is an artificial construct that means not much at all really. I do have favourite bowling ball reactions though and companies that make gear that gives me those reactions get my attention.
Different ball companies use different materials and core designs that they have a lot of money tied up in the development of. Consequently, they get variations on a theme in their product range and the customer gets an idea of what to expect from that company. It's a bit like the way architects end up making variations of the same house again and again. The architect knows the design and gets customers who have already seen one like it and want another.
Vested interest declaration here - I'm sponsored by Storm and like their gear because it gives me a variety of backend reactions. If I didn't like the gear, the sponsorship would be worthless to me. The Agent line is rolly, like some companies, the Premier and Fire lines are more angular, like others. All the gear seems to respond readily to different layouts giving me the opportunity to really fine tune the reaction when I drill the ball. There's a wide range to keep me competitive in a lot of places so long as I throw it well.
The clincher for me is that Storm balls clear the heads well and stay alive down lane, allowing me to play from way out to way in and still be able to find an angle to strike from places I see a lot of folks leaving the weak 10.